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Outline

Introduction Basic idea of low temperature detectors Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs Direct Search for WIMPs, Search for ββ 0 ν Low temperature detectors at KRISS X-ray sensors Prospective R & D. Outline. Light detector.

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Outline

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  1. Introduction Basic idea of low temperature detectors Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs Direct Search for WIMPs, Search for ββ0ν Low temperature detectors at KRISS X-ray sensors Prospective R & D Outline

  2. Light detector Solid State Detectors Thermometer Thermometer Charge collector Scintillator Semiconductor Measurement methods (Charge, Light, Temperature) “Low temperature favorable”

  3. Basic idea: Calorimetric detection X-ray, e-, WIMP, etc. Thermometer Absorber Thermal link Heat sink < 100 mK Choice of thermometers TES, MMC, Thermistor, STJ, KID etc.

  4. High resolution Low threshold Why Low Temperature Detectors? • Advantages of using cryogenic calorimeters • Extreme sensitivity of energy resolution (ΔE/E < 1/1000) • Ultra low energy threshold ( < 1 eV) • Active for Charge, Light, Phonon chains 240g sapphire (CRESST-I)  580 eV at 10 mK, 99% efficiency Counting 1.5μm(0.8 eV) photons(NIST)

  5. What to measure? • WIMP: CDMS, CRESST, EDELWEISS, etc. • Nutrinoless double beta decay: COURICINO(COURE) • Direct measument of neutrino mass: MARE • Absolute measurement of radioactivity • X-ray astronomy: Constellation-X, XEUS • Energy Depressive x-ray spectroscopy • γ-ray spectrometer • Single photon counting: IR, visible, UV, etc. • Bio-molecules: time-of-flight mass spectrometry

  6. Thermistors • Neutron transmuted doped Ge thermistors • Ion implantation doped Si thermistors • Near metal-insulator transition • R(T) : 1 M ~100 M • Operated with conventional electronics • Slow due to poor coupling between conduction electrons and lattice of the thermistor • E dependent resistance • Radioactive contamination (68Ge, 3H)

  7. I ΔI t Transition Edge Sensor (TES) (초전도상전이센서) • Superconducting strip at Tc • (W, Ir/Au, Mo/Au, Mo/Cu,Al/Ag, etc.) • RN : 10 m ~1  • Proximity effect : Tunable Tc (20~200mK) • Voltage Bias  negative feedback working point TES

  8. g = 6.8 Metallic Magnetic Calorimeter (MMC) (자기양자센서) Field coil Magnetic material (Au:Er) in dc SQUID • Au:Er(10~1000ppm) • weakly-interacting paramagnetic system • metallic host: fast thermalization ( ~ 1ms) junctions 50 G  Δε= 1.5 eV 1 keV  109spin flips Absorber Au:Er SQUID Loop Si

  9. Different sensors TES MMC Thermistor • Neutron Transmuted Doped Ge • Ion Implantation Doped Si • ΔE: 3.2 eV @ 6 keV Superconducting strip at Tc (W, Ir/Au, Mo/Au, Mo/Cu) ΔE: 1.8 eV @ 6 keV Magnetic material (Au:Er) in a SQUID loop ΔE: 2.7 eV @ 6 keV Fast, Wide working temp. Absorber friendly MUX being developed I of 167Er Conventional electronics Absorber friendly Slow at low temp. Joule Heating Fast, Most sensitive MUX possible Narrow working temp. High-tech. fab.

  10. Introduction Why? How? What? Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs Direct Search for WIMPs, Search for ββ0ν Low temperature detectors at KRISS X-ray sensors Prospective R & D Outline

  11. CDMS, EDELWEISS, CRESST High resolution, Low threshold Active background rejection Direct Search for WIMP using LTDs

  12. CaWO4 electron recoils (e-s, γ‘s) CRESST Energy in light channel (keVee) nuclear recoils (neutrons) Energy in phonon channel (kev) electron recoils (γ‘s) Energy in charge channel (keVee) nuclear recoils (neutrons) Energy in phonon channel (kev) Background rejection Nuclear recoil on electron recoil bkg Light Charge Phonon Different Ch/Ph or L/Ph ratio for electron recoils and nuclear recoils Event by event discrimination

  13. e- e- Neutrinoless ββ decay with LTD Double Beta Decay with two neutrinos (Rare Spontaneous Nuclear Transition) Double Beta Decay with no neutrino Calorimetric Detection Source ≡ Detector (only neutrinos are allowed to escape from the bulk)

  14. COURICINO toward COURE COURICINO (40.7 kg of TeO2 + NTD Ge) 130Te : candidate for ββ-0ν natural abundance (34%) high transition energy (2.53 MeV) 5cm (2006) COURE (741 kg TeO2) plans to start data taking early 2010

  15. Introduction Why? How? What? Sensor comparison (Thermistors, TES, MMC) Low temperature detectors in underground labs Direct Search for WIMPs, Search for ββ0ν Low temperature detectors at KRISS X-ray sensors Prospective R & D Outline

  16. First signal at KRISS for rare events 2006/06 S.C. Kim 6 keV from 55Fe Counts cosmic ray 5×5×0.5 mm3 Si with Ti/Au TES WIMP, ν, 0νββ etc. Signal size (a.u.) Clear appearance of 6 keV x-rays Important demo. toward massive detectors

  17. Detector development at KRISS MMC TES Au:Er Si field coil SQUID loop 18 eV FWHM 55Fe spectrum Measured with MMC 2007/11/09, S.J. Lee Mn Ka2 Mn Ka1

  18. R & D plan at KRISS Scintillating Detectors for 0νββ at Low temperatures Two detection channels phonon + light TES Si or Ge Additional light sensor CaMoO4 Phonon sensor w. TES or MMC

  19. Comparison with COURE ~ 1/3000 ?? Y2L ??

  20. Staffs Yong-Hamb Kim(김용함) Kyoung-Bum lee(이경범) Minkyu Lee(이민규) Post docs and students Young-Hwa Lee (이영화, post doc) Yong-Dae Kwon (권용대, post master) Sang-Jun Lee (이상준, PhD candidate, SNU) Hwa-Yong Lee (이화용, PhD Candidate, Kongju U.) LTD People at KRISS A few positions available for students and post-docs If interested, talk to us.

  21. Thank you (감사합니다)

  22. Extra slides

  23. Phonon signals Phonon down conversion 1. Very high energy phonon (not stable) Anharmonic decay ~ ns 2. 20 ~ 50 K phonon (stable) Athermal signals: TES, MMC, NbSi Inelastic surface scattering Inelastic impurity scattering ~ 10 μs 3. Thermal phonon distribution Thermal signals: NTD, TES, MMC Size and shape of athermal signals also provide discrimination for surface events

  24. Cryogenic massive detectors

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